This application claims priority of the German patent application 101 44 048.0 filed Sep. 7, 2001 which is incorporated by reference herein.
The invention concerns an apparatus for handling coverslips for specimen slides, the apparatus comprising a base block, a transport arm on which the base block is mounted, and at least two pickup means provided in the base block, each pickup means having an end that comes into contact with the coverslip, and each of the ends pointing away from the notional center axis of the base block.
The invention furthermore concerns a method for removing coverslips and placing them onto a specimen slide, the coverslips being deposited in a magazine.
An automatic cover slipper is used to automatically position coverslips on a microscopy specimen slide and to cover a preparation present on the specimen slide. Coverslips of a wide variety of sizes are available in packages, usually of 100 units. Before the coverslipping operation, a single coverslip must be removed from a stack. This step is very critical, since the coverslips can adhere to one another because of their thinness (approx. 0.17 mm thick) and smooth surface. A further problem is glass breakage. The stack of coverslips sometimes contains broken coverslips, but manipulation in the coverslipper can also result in glass breakage. The existing art described below is not capable of proposing any solution to this problem.
Patent application WO 97/00461 discloses an apparatus for picking up and depositing coverslips. The pickup head comprises two suction cups pointing downward and outward at an angle. The coverslip assumes a concavely curved shape when it is being held by the suction cup. Provided between the suction cups is a piston that is preloaded by a spring and can be brought by a magnet coil into a position such that the piston does not touch the coverslip held by the suction cups. Once a coverslip has been picked up, if the piston is retracted by the magnet coil, a slight warping is exerted on the coverslip and detaches any further coverslips that may be adhering. A separate deposition head, which retains the coverslip with a suction cup and guides it over the specimen slide, is provided for deposition of the coverslip onto the specimen slide. The coverslip is pressed onto the specimen slide with a pivotably mounted lever and lastly deposited onto it. This apparatus for picking up and depositing coverslips disclosed here possesses a special configured head for each operation. This in turn increases the probability of damage to the coverslips being deposited.
WO 95/20176 discloses an instrument for automatic deposition of coverslips. The pickup head possesses suction cups, facing outward from the longitudinal axis of the pickup head, to which a vacuum can be applied individually. A piston that is mechanically preloaded downward with a spring is provided between the suction cups. In order to pick up a coverslip, the pickup head is pressed onto the coverslip stack until the suction cups are in contact with the topmost coverslip. The adhesion between the topmost coverslip and the coverslips below it is overcome by means of a shearing motion. As soon as the pickup head has completely grasped the coverslip, it transfers it to a deposition head that then deposits the coverslip onto the specimen slide. The high mechanical stress, the transfer of the coverslip from one station to a subsequent one, and the absence of automatic monitoring mean that this system cannot operate with sufficient confidence. It also definitely requires more frequent service as a result of its complexity.
An apparatus that both removes coverslips from a cover glass stack and deposits them onto a specimen slide is disclosed in U.S. Pat. No. 4,428,793. The apparatus comprises a pickup element and a first and second pushing element. The pickup element is configured as a suction cup, and the first and second pushing means engage at opposite ends of the coverslip. Upon removal of the coverslip from the coverslip stack, it is curved by the action of the first and second pushing elements, and thus detached from the coverslips adhering below. The high mechanical stresses as coverslips are picked up from the stack and deposited onto the specimen slide increase the probability of coverslip breakage, which negatively influences the efficiency of the apparatus.
It is the object of the invention to create an apparatus with which coverslips can be automatically removed from a coverslip stack and the risk of coverslip breakage is considerably reduced. A further intention is that deposition of the coverslips onto the specimen slide be accomplished as automatically as possible and without disruptions.
This object is achieved in that the base block provided on the transport arm in each case both removes a single coverslip from a magazine, and deposits the removed coverslip onto a specimen slide.
A further object of the invention is to create a method which makes possible reliable, accurate, and economical deposition of coverslips onto specimen slides.
This object is achieved by way of a method characterized by the following steps:
lowering a transport arm with a pivotable base block mounted thereon, at least two pickup means being provided in the base block, each pickup means comprising an end that comes into contact with the coverslip and each of the ends pointing away from the notional center axis of the base block;
picking up a coverslip with the ends of the pickup means, the coverslip resting against a continuously and uniformly curved surface of the base block; and
lowering the transport arm onto the specimen slide, in which context the continuously and uniformly curved surface of the base block rolls onto the specimen slide and deposits the coverslip.
It is advantageous that with the apparatus, once the coverslip has been picked up from the magazine it need not be set down again or transferred to a further device for depositing the coverslips onto the specimen slide. This considerably reduces the risk of coverslip breakage. In addition, the apparatus works more effectively as a result. More specimen slides per unit time can be equipped with coverslips.
A further advantage is constituted by the fact that the base block of the apparatus comprises a continuously and uniformly curved surface beyond which the ends of the pickup means project. A defined contact of the coverslip is thereby achieved. In addition, contact in this form means that no points or edges are formed that would exert excessive pressure on the coverslip. A uniformly distributed force thus acts on the coverslip. Means for reducing the length of the pickup means are provided, so that as a result of the reduction in length, the coverslip is brought into contact with the continuously and uniformly curved surface. A particularly uniform distribution of force is obtained if the continuously and uniformly curved surface corresponds to the curved surface of a cylinder segment. In equally low-stress fashion, the base block is connected to the transport arm pivotably via an articulated joint.
In order to ensure automation of the apparatus, there is provided in the base block, between the at least two pickup means, a sensor which ascertains the presence and the condition of a coverslip that has been picked up. It is thereby possible to prevent broken coverslips from being deposited onto the specimen slide.
It is advantageous that the pickup means is configured as suction device; and that a suction cup is provided on each of the ends of the pickup means coming into contact with the coverslip.
In a particularly advantageous embodiment of the invention, the means for reducing the length of the pickup means is configured as a bellows. Upon application of a negative pressure, a coverslip that has been picked up is thus brought into contact with the continuously and uniformly curved surface of the base block.
Movability of the apparatus is ensured by the transport arm, which comprises a support element that is arranged substantially parallel to the surface of a specimen slide, an angled element movable linearly along the support element, and a lifting element movable along one limb of the angled element. The lifting element carries the base block at an end opposite the coverslips.